This document discusses subsidence, including its causes, signs, impacts, and prediction. It defines subsidence as the vertical downward movement of a building foundation, usually caused by loss of ground support below. Key signs of subsidence include cracking in walls and around openings. Causes mentioned include settlement after construction, thermal expansion/contraction of materials, chemical attack, roof spread, and wall tie failure. Impacts can include increased flood risk and damage to buildings. The document also distinguishes subsidence from settlement and discusses the soil ripening process and subsidence of organic soils.

1. SUBSIDENCE
PREDICTION
P r e s e n t e d b y :
M d . F a y e z u r R a h m a n
D e b a r s h i C h o u d h u r y
M d . R o k o n U d d i n
M d . O m a r J a b e r
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2. What is the subsidence?
 It is the vertical downward movement of a
building foundation.
 Generally caused by the loss of support of the
ground beneath the foundations.
 It results in cracking and hence property
damage.
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3. Subsidence
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4. Signs of Subsidence
 Vertical and diagonal cracking concentrated
in specific areas.
 Tapering in width between the top and
bottom of the crack.
 Cracks extending through the damp proof
course (DPC) down into the foundations.
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5. Signs of Subsidence
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6. Signs of Subsidence
 External cracking reflected internally in the
same area of wall.
 Rucking of wallpaper at corners between
walls and ceilings.
 Distortions of openings causing doors and
windows to stick.
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7. Signs of Subsidence
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8. Causes of Subsidence
 Settlement after construction
 Thermal expansion and contraction of
materials
 Chemical attack
 Roof spread
 Wall tie failure.
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9. Impact of subsidence
 Increased flood risk.
 Damage to buildings, foundations,
infrastructure and subsurface structures.
 Disruption of the water management and
related effects.
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10. Impact of subsidence
 Increased CO2 emissions due to accelerated
oxidation of peat areas;
 Nutrient leaching;
 Reduction in biodiversity and ecological
value.
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12. Settlement and/or Subsidence
 Settlement is where the
structure moves the
soil due to application
of load.
 Settlement normally
occurs early in the life
of a property
 the supporting soil
moves away from the
structure taking away
its support and
allowing the structure
to move is called
settlement.
 subsidence can occur
at any time
Settlement Subsidence
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13. Settlement or Subsidence
 Settlement is not
covered by insurance
 Settlement usually
occurs in new or
relatively new
buildings
 Impact of settlement is
less worrying then
subsidence.
 Subsidence is normally
covered by insurance
 Where's subsidence
occurs in relatively
older buildings
 In other words, impact
of subsidence is more
worrying than
settlement
Settlement Subsidence
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14. Settlement or Subsidence
Settlement Subsidence
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15. The Soil-Ripening Process
 A freshly-deposited mud is transformed into a
dryland soil.
 The process is also called initial soil formation
or initial pedogenesis.
Mainly 3 Types:
1. Physical ripening
2. Chemical ripening
3. Biological ripening
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16. Physical ripening
Physical ripening, which mainly comprises
physical symptoms
 directly related to the irreversible dehydration
of the soil.
 It involves changes in the soil’s water content,
volume, consistency, and structure.
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17. Chemical ripening
Chemical ripening, which comprises all
chemical and physicochemical changes. Such as
changes in the-
 Quality and quantity of absorbed cations of the
adsorption complex
 Reduction and oxidation of iron sulfides
 Changes in the organic matter content etc.
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18. Biological ripening
Biological ripening, which comprises aspects of
the ripening process Influenced by organisms.
For example,
the number of bacteria species,
 vegetation,
oxidation of organic matter, etc
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19. Subsidence of Organic Soils
Combination of oxidation and irreversible
shrinkage.
 Oxidation means conversion of organic
carbon to carbon dioxide
 Shrinkage - the decrease in porosity due to the
loss of soil water as a result of physical
ripening.
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20. Subsidence of Organic Soils
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21. Subsidence of Organic Soils
 Organic soils (or Histosols) are classified by
their organic matter content.
 They are subdivided into
 peat soils
 muck soils
 organic soils and
 mineral soils.
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22. In a subsidence emergency
 Determine if your building is served by
natural gas and if so, contact the Public
Service Company.
 Contact your city or country safety
department/fire department and the Office
of Surface Mining (OSM).
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23. In a subsidence emergency
 Contact your city water and sewer
department so that these lines can be checked
for damage.
 If the subsidence feature is near the house,
large windows should be taped to help
prevent flying glass, should distorted windows
shatter.
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